A boot band is used, for example, as a constant-velocity joint that transmits the drive power of an engine from a drive shaft to a driven shaft. In a constant-velocity joint, a drive-power transmission portion is covered by a bellows-like boot, and grease is retained inside the boot. A boot band is wound around the outer periphery of both ends of the boot and is reduced in diameter, whereby the boot band clamps the boot so as to prevent the grease from leaking out of the boot. A pair of boot-band pawls are provided on such a boot band so that a clamping tool can be hooked onto the boot-band pawls to clamp the boot band, whereby clamping force is applied via the pair of the boot-band pawls in the direction to reduce the diameter of the boot band.
FIG. 12 shows a prior-art boot band 1. The boot band 1 comprises a band body 3 made of a thin metallic plate. The boot band 1 is wound in a ring-like form so as to clamp a member, such as a boot, in such a way that the boot band is wrapped completely around that member. When the band body 3 is wound around that member, winding is done in such a way that the outer-layer portion of the band body 3 overlaps the inner-layer portion of the band body 3. Thereby, the band body 3 has an outer-layer portion 4 and an inner-layer portion 5 that overlap each other.
As shown in FIG. 12(a), a first boot-band pawl 7 is formed on the top of the outer-layer portion 4 of the boot band 1, and a second boot-band pawl 6, which forms a pair with the first boot-band pawl 7, is formed on the inner-layer portion 5 of the boot band 1. These boot-band pawls 7, 6 are used for clamping the ring-like formed band body 3 in the diameter-reducing direction, and the claw portions of a clamping tool (not shown) are hooked onto those boot-band pawls 7, 6.
The second boot-band pawl 6 is press-molded so as to rise outward in the radial direction, and an opening 6b, which opens toward the first boot-band pawl 7, is formed in the second boot-band pawl 6, and the outer wall of the opening 6b forms a pressing part 6a. In addition, in the outer-layer portion 4, a portion that is closer to the top end (free end) of the outer-layer portion 4 of the boot band 1 than is the first boot-band pawl 7 serves as a terminal end 14 and extends in a flat form. This terminal end 14 is inserted into the second boot-band pawl 6 through the opening 6b. The terminal end 14 that is inserted into the opening 6b is pressed by the pressing part 6a so as to prevent the terminal end 14 from lifting outward in a radial direction. Because the terminal end 14 at the top end of the outer-layer portion 4 is inserted into the second boot-band pawl 6 so that the top end (terminal end 14) of the outer-layer portion 4 is pressed by the pressing part 6a, it is not necessary to press the outer-layer portion 4 inward at the time of clamping. Therefore, clamping of the member to be clamped is done simply by clamping the boot band in the diameter-reducing direction. In other words, clamping is performed by one action, which improves clamping workability. Patent Document 1 (Japanese Patent No. 4403728) discloses a boot band in which, as is the case with the boot band of FIG. 12, the second boot-band pawl presses the terminal end provided at the top end of the outer-layer portion, so that clamping is performed by one action.
In the prior-art boot band, as shown in FIG. 12(a), multiple engagement holes 12, 13 are formed in the lengthwise direction in the outer-layer portion 4, and an engagement pawl 11 that engages with either of the engagement holes 12, 13 is formed in the inner-layer portion 5 of the boot band 1. The engagement pawl 11 rises in a slope-like form facing the top end of the outer-layer portion 4 of the boot band 1. FIG. 12(a) shows a band body 3 in a ring-like form in a temporarily-locked condition. In this temporarily-locked condition, the engagement pawl 11 engages with a top-end engagement hole 12 located at the top of the outer-layer portion 4. Under this condition, applying a clamping force F (see FIG. 12(b)) to the band body 3 in the diameter-reducing direction causes the top-end engagement hole 12 to be moved over the engagement pawl 11, and then the engagement hole 13, which is behind the top-end engagement hole 12, engages with the engagement pawl 11. Due to this engagement, the band body 3 maintains a diameter-reduced condition whereby the diameter of the boot band is reduced and the member to be clamped is clamped.
The above-mentioned prior-art boot band 1 has a problem that the inner-layer portion 5 of the boot band 1 might buckle when the band body 3 is clamped. How such buckling can occur will now be described with reference to FIG. 12.
FIG. 12(a) shows a state where the engagement pawl 11 is engaged with the top-end engagement hole 12, so that the band body 3 is in a temporarily-locked condition in a ring-like form. Under this condition, when a clamping tool is used to apply clamping force F to the band body 3 in the diameter-reducing direction, the top-end engagement hole 12 slides on the back face 11a of the engagement pawl 11 and climbs over the engagement pawl 11, as shown in FIG. 12(b). At the time of this moving-over, the rear of the top-end engagement hole 12 in the outer-layer portion 4 gets stuck with the back face 11a of the engagement pawl 11, as a result of which the sliding of the top-end engagement hole 12 is stopped and locked.
Because the sliding is stopped, a load that should have been used for reducing the diameter of the band body 3 is applied to the portion between the engagement pawl 11 and the second boot-band pawl 6 in the inner-layer portion 5. Under this condition where the sliding of the top-end engagement hole 12 is stopped and locked, even when a clamping force F is applied to the band body 3, the condition becomes the same as that when the load of the clamping force F is received by the inner-layer portion 5 between the engagement pawl 11 and the second boot-band pawl 6 in the inner-layer portion 5. When the clamping load on the band body 3 exceeds the buckling-resistance capability of the band body 3, resulting in an overload state, buckling 16 occurs in the inner-layer portion 5 between the engagement pawl 11 and the second boot-band pawl 6 in the inner-layer portion 5 (see FIG. 12(c)).
Patent Document 1 discloses a boot band having a structure in which the second boot-band pawl 6 presses the terminal end provided at the top end of the outer-layer portion 4 so that clamping is performed by one action (as is the case with the boot band of FIG. 12), thereby preventing the aforementioned occurrence of buckling in the inner-layer portion 5. In the invention of Patent Document 1, a slit or the like is provided between the top-end engagement hole 12 and the first boot-band pawl 7 in the outer-layer portion 4, so that the rigidity of the outer-layer portion 4 between the top-end engagement hole 12 and the first boot-band pawl 7 is reduced. As a result of this reduction of the rigidity, when the band body is clamped the outer-layer portion 4 is allowed to slide so as to press the portion between the engagement pawl 11 and the second boot-band pawl 6 in the inner-layer portion 5; in addition, the load by which the outer-layer portion 4 presses the back face 11a of the engagement pawl 11 toward the center of the ring-like form is reduced, thereby preventing buckling 16 of the area between the engagement pawl 11 and the second boot-band pawl 6 in the inner-layer portion 5.
Also, Patent Document 1 discloses that a rib or the like is formed between the second boot-band pawl 6 and the engagement pawl 11 in the inner-layer portion 5, so that the rigidity of the inner-layer portion 5 between the second boot-band pawl 6 and the engagement pawl 11 is increased so as to increase the buckling-resistance capability of the boot band, thereby preventing buckling at the portion of the inner-layer portion 5 between the engagement pawl 11 and the second boot-band pawl 6 in the inner-layer portion 5.